Improving readability (contrast) of the UI

[ghost]

Since the game's current theme means rather bright colors on the maps, the white UI can be hard to read at a glance. To improve this, we could:

• put drop shadows behind all the elements,

  • alternatively put a simple outline around them;
    
    

• add gradient bars (I personally find this option to be least intrusive),

  • here shown only on the bottom, but a matching or even symmetrical bar on top may be desirable as well (for chat and system messages, this would also allow a redesign of the score bar);
    
    

• add permanent vignette, and only color it red when receiving damage,

  • currently only a red vignette appears briefly after receiving damage.
    
    

How exactly they should look is up for debate (sizing, gamma…).
Apologies for small glitches in the images, I didn't notice them when working in a smaller window.